Joint compounds are commonly used to fill and smooth the joints between abutting edges of adjacent gypsum wallboards and to patch damaged wallboard. Typically, joint compounds are applied to the aforesaid joints or wallboard, often over a tape or mesh support, in a manner that hides the joints or damage, thereby providing a smooth and uniform appearance thereto.
Generally, there are two types of joint compounds: dry and ready-mix. Dry joint compounds, as their name implies, require the addition of water to their dry components prior to use. After the addition of water, this type of joint compound must be used relatively quickly, within minutes to hours, and cannot be stored in a wetted condition. In contrast, water is added to the components of ready-mix compounds during manufacturing, providing compounds that may be stored in a wetted state for months until needed. Ready-mix compounds are thus preferred by many users because they require little or no water to be added to the compound prior to use.
Ready-mix compounds may be conveniently segregated into two groups based on their method of cure: drying type and setting type. Drying type compounds cure upon the loss of water due to evaporation, while setting type compounds cure as a result of a chemical reaction that occurs between calcined gypsum (calcium sulfate hemihydrate) and water. While the ready-mix compounds contain water, the hydration reaction in the setting type compounds is inhibited by the inclusion therein of a set retardant. The inhibiting effect of the set retardant is commonly overcome by the addition of an activator to the uncured setting type compound just prior to use, whereby the curing of the compound is initiated.
While existing ready-mix joint compounds provide certain acceptable properties and performance, a need exists for joint compounds which provide enhanced properties and/or performance relative to existing compounds.